CANANDAIGUA, N.Y. — Investigators have yet to find any evidence of criminal behavior by NASCAR veteran Tony Stewart in the death of a young dirt-track racer, after authorities concluded reconstruction of the crash at the track, an official said on Monday.

Stewart, a mercurial three-time NASCAR champion, and one of the sport’s biggest names, struck and killed 20-year-old Kevin Ward Jr. after he walked onto the track and apparently lashed out at Stewart after he caused his car to spin out during a race Saturday in upstate New York.

The 43-year-old driver was “grieving,” his publicist said, and had not decided whether he will return to competition after dropping out of a NASCAR race on Sunday.

The crash, recorded on video that went viral online, raised questions about safety and lighting at the track, whether Stewart could have avoided Ward and whether the aggressive, often brazen, behavior that is part of the sport of racing was to blame.

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An autopsy on Monday revealed that Ward, a Sprint-car driver, died of “massive blunt trauma,” but gave no other details, Ontario County Sheriff Phil Povero said.

After completing the crash reconstruction at the 61-year-old Canandaigua Motorsports Park in the small New York town, Povero said the investigation was still open.

“At this time, there are no facts that exist that support any criminal behavior or conduct or any probable cause of a criminal act in this investigation,” Povero said at a news conference, adding that there was no timeline to conclude.

Ward, whose website said he began racing go-karts at age 4, was spun into an outside wall after bumping cars with Stewart, a temperamental driver who has had several off-the-track scuffles with other drivers.

As the caution flag went out, Ward left his car apparently in an attempt to confront Stewart, whose car remained on the track. When Ward angrily pointed at Stewart on the next lap, Stewart’s car wobbled slightly, striking Ward.

‘A terrible tragedy’

Following the accident, Stewart decided not to race the next day at Watkins Glen, a NASCAR track about an hour’s drive from Canandaigua. His status for the Michigan 400 on Sunday has not been determined.

“The decision to compete in this weekend’s NASCAR Sprint Cup Series event at Michigan will be Tony’s, and he will have as much time as he needs to make that decision,” the multimillionaire driver’s publicist, Mike Arning, said in an email to Reuters.

“It is still an emotional time for all involved, Tony included. He is grieving, and grief doesn’t have a timetable.”

Plymouth Speedway released a statement on Monday announcing that Stewart will not compete in this Saturday’s dirt-track race in Plymouth, Indiana.

“We at Plymouth Speedway extend our deepest condolences and prayers to the family of Kevin Ward Jr. and thoughts and prayers to Tony Stewart and his family,” the statement read. “Tony Stewart will not be racing at Plymouth Speedway this Saturday.”

A small tribute of daisies and sunflowers was set up on Monday at the New York track.

Race fan Jim Natoli, 66, of nearby Manchester, New York, was surrounded by news crews as he stopped to pay his respects.

“It’s a very safe track,” he said. “They have races here every week. It’s a terrible tragedy.”

“This was like a perfect storm,” Andretti, winner of the Formula One World Championship, the Indianapolis 500 and NASCAR’s Daytona 500, told Reuters in a telephone interview. “You could look around and say this could have been avoided — yes, by everyone. It’s tragic, but you can’t fault the sport for it.

“He [Ward] walked out of the car; he looked fine. This is something that happened and hopefully this will never, ever happen again,” Andretti said.